The present invention relates to a coupled laser diode arrangement of two laser diodes in a layered format.
It is known to provide a plurality of p-n laser diodes in a common semiconductor body with their respective, laser-active zones in proximity such that a (respective) spacing of strip-shaped laser-active zones from one another is so small that wave-mechanical coupling of the laser radiation occurs in the individual strip-shaped zones.
Such a wave-mechanical coupling is exploited, for example, for generating monomode laser radiation. A control is also achieved of the laser beam generation in one zone by intensity variation and/or modification of the excitation conditions of the laser radiation in the other, proximate zone. For example, Jap. Journ. Appl. Phys., Vol. 17 (1978), pages 751-752 and Journ. Quantum Electr., Vol. QE 13 (1977), pages 619-622, both incorporated herein by reference, disclose arrangements which comprise a respective first and second zone lying on top of one another. Although laser radiation proceeds in both zones, radiation generation due to current flux through a p-n junction of the layer structures only occurs in the first zone. The other, second zone is a passive optical resonator which is wave-mechanically coupled to the first zone containing the p-n junction. The effective band space in the material of this second zone, i.e. in the zone of the passive resonator, is greater than that in the first zone having the p-n junction. If laser radiation were to be generated in this second zone, its frequency would be different from, namely higher, than the frequency of that laser radiation which is in fact generated in this known arrangement, namely in the first zone thereof comprising the p-n junction. The intended wave-mechanical coupling, though, would be impossible, i.e. the passive property of this second zone is of decisive significance for this prior art.
Array arrangements having mutually coupled strips which generate laser radiation, i.e. having mutually coupled laser diodes, are also known, and are provided in or on a semiconductor body. With respect to further details relating to such known arrangements, see "Appl. Physics Letters", Vol. 42 (1983), pages 152-154 and Vol. 43 (1983), pages 521-523; "Fourth Intern. Conference on Integrated Optics and Optical Fibre Communication", June 27-30, 1983, Tokyo; IEEE Journ. of Quantum Electronics", Vol. QE 18 (1982), pages 1679-1688; "Appl. Physics Letters", Vol. 41 (1982), pages 112-114; U.S. Pat. No. 4,347,612; U.S. Pat. No. 4,101,845; and U.S. Pat. No. 4,277,762. Further technological background to the present invention is specified in "IEEE Spectrum" (1983), pages 38-45. All of the above references are incorporated herein by reference.
The longitudinal series placement and the lateral juxtaposition of respective laser-active zones or laser diode strips in an arrangement on or in a substrate body is known from the above publications. The essential problem for the manufacture of such an arrangement is the adjustment of these zones or lasers relative to one another, since even slight spacing deviations have considerable influence. Also, an added problem in index-guided laser diodes is that the spacing dimensions coming into consideration are extremely small due to the low width of the wave-mechanical or wave-optical near field of the laser radiation. The laser diodes are usually laser diodes of the double-hetero structure type of, for example, indium-gallium-arsenide-phosphide/indium phosphide. Particularly given laser diodes of this type, two laser diodes to be coupled to one another can be disposed at a slight distance from one another, even given execution as index-guided laser diodes.